BackgroundThis paper reviews current knowledge about the developmental outcomes of children with auditory neuropathy/auditory dyssynchrony (ANAD).AimThe article discusses the diverse variables that can impact developmental outcomes of this population of children with hearing loss and what is currently known in the literature. Since two-thirds of the children with ANAD have additional disabilities, this population of children is very complex.PatientsThe article discusses three children with very diverse developmental profiles including the differential diagnostic evaluations that supported decisions about communication approaches.MethodsThree case histories of children with ANAD representing different individual characteristics and developmental trajectories are discussed. These three cases were chosen to represent the diversity of the population of children with ANAD.ResultsCase A is a child who received bilateral cochlear implantation and successfully developed listening and spoken language skills. Case B is a child who received bilateral cochlear implantation which did not result in successful listening and spoken language because of a breakdown at the level of the auditory cortex but is using sign language as a primary approach to learn to communicate. Case C is a child with significant co-morbidities including cerebral palsy and global developmental delays who is communicating through both spoken and signed language without the use of amplification.ConclusionChildren with ANAD have significant diversity in their ability to access spoken language without amplification, with hearing aids and with cochlear implants. However, despite this diversity, when children are provided access to language through individualization and appropriate matching of both auditory and visual communication approaches, they can become successful language learners.

This article discusses the developmental outcomes of children with auditory neuropathy or auditory dyssynchrony (ANAD), also referred to as auditory neuropathy spectrum disorder (ANSD). These children constitute an extremely complicated and diverse group. An excellent resource for the definition of ANSD can be found in the document Identification and Management of Infants and Young Children with Auditory Neuropathy Spectrum Disorder from the Guidelines Development Conference, Newborn Hearing Screening, NHS, Como, Italy [1] . This document provides an excellent overview of the definition of the disorder and its diagnostic audiologic evaluation.

Characteristics of auditory neuropathy or auditory dyssynchrony that could impact spoken language outcomes

Teagle et al.[2] reported on a prospective longitudinal study of 142 children with ANSD, of whom 52 had undergone cochlear implantation (CI) with a mean duration of use of 41 months. An overall 42% of the children were born prematurely, often with multiple comorbidities; 81% had more than a severe degree of hearing loss (>70 dBHL); 38% had abnormal findings on MRI of the brain and inner ear; and 50% of them achieved open-set discrimination. Thirty percent of those with more than 6 months of experience with CIs were unable to participate in this testing because of developmental disabilities or age constraints. No child with cochlear nerve deficiency achieved open-set discrimination in this study. They concluded that the population of children with ANSD is a diverse group, with some children unable or unlikely to benefit from CI or conventional amplification. They concluded that electrical-evoked intracochlear compound action potentials may provide information about children who might benefit from auditory input for spoken language development.

Gardner-Berry [3] reported that, in a population of 850 children with CIs, 6% of children with sensorineural hearing loss had cochlear abnormalities as compared with 16% of children with ANSD; 55% of children with ANSD had normal auditory nerves, whereas 20% had bilaterally abnormal auditory nerves and 6% unilaterally. Gardner-Berry et al. [4] discussed the use of transtympanic electrical auditory brain stem response as a measure of auditory neural survival for transmission of auditory stimuli.

Walton et al. [5] reported that among 54 children with ANSD and CI, 28% had compromised auditory nerves. Of the 39 children with normal cochlear nerves, 79% had comorbidities and 8% had inner ear abnormalities. Of the 15 children with compromised cochlear nerves, 67% had comorbidities and 93% had inner ear abnormalities. In addition, in five children with normal-sized internal auditory canal, the cochlear nerve was compromised, highlighting the need for transtympanic electrical auditory brain stem response assessment. A total of 14 of the 15 children (93%) with compromised nerves had other structural abnormalities. Fifty-one different abnormalities were identified in 30 ears, which included incomplete partition of the cochlea, hypoplasia, enlarged and/or fused vestibule, hypoplasia/aplasia of the vestibule or fusion of the lateral semicircular canals with the vestibule, dilated endolymphatic duct or sac, or dilated vestibule aqueduct.

The research on structural abnormalities indicates that there is a higher percentage of children with both auditory nerve and cochlear abnormalities among children with ANAD/ANSD than among children with sensorineural hearing loss. Potential for auditory spoken language through the use of hearing aids or CIs can be compromised when the child has structural abnormalities.

Research also highlights the high proportion of children with comorbidities, indicating that a significant population of children with ANAD/ANSD could be at risk for cognitive and neurological issues that compromise the processing of auditory spoken language.

Cortical auditory evoked potentials of children with auditory neuropathy or auditory dyssynchrony

Rance et al.[6] performed cortical auditory evoked potentials (CAEP) on school-aged children with ANAD who were fitted with conventional amplification aids. Children with present P1s demonstrated speech discrimination scores greater than 30%, ranging from almost 40% to almost 100%, with an average of 60%. Children with absent P1s demonstrated speech discrimination below 30%, averaging about 10%. CAEP can be a part of the diagnostic evaluation protocol for decision-making for conventional amplification and CI.

Rance (2008) reported a study on 39 children: 10 with ANAD fitted with hearing aids, 10 with ANAD with implantation, nine with ANAD with implanted electrically evoked auditory brain stem response (EABR), and 10 children with sensori-neural hearing loss (SNHL). He found no significant difference when comparing children's speech perception under noise conditions. They required a 20 dB signal to noise ratio in order to perform as well under noise as under quiet conditions. Thus, children with ANAD when successful with speech perception still have challenges in noisy situations, such as classrooms.

[TAG:2]Characteristics of children with auditory neuropathy or auditory dyssynchrony from the Colorado population 2002-2009

[TAG:2]Data from the State of Colorado Home Intervention Program (CHIP) provide information on longitudinal development of children identified with hearing loss during the first 3 years of life. Most of the children are identified through universal newborn hearing screening. Since the screening of birth cohorts from 2002 to 2009, there have been many changes and increased knowledge on the diagnosis and treatment of children with ANAD. The Colorado Hearing Screening Program shows records for 67 infants diagnosed with ANAD from a population of 610 829 infants screened from a birth population of 626 701 during the years 2002-2009 [18],[19],[20],[21],[22],[23] . A total of 873 children were identified with sensorineural hearing loss. The incidence of hearing loss ranged from 1.6 to 1.8 children for every 1000 births. ANAD was seen in about one child in every 10 000 births.

Most of the children with ANAD were identified with bilateral ANAD (79%) and 21% were identified with unilateral ANAD [18] . Ninety percent of the children identified with ANAD were those who had spent time in the Newborn Intensive Care Unit (NICU). Only 10% of the children identified with ANAD were from the well-baby nursery. Of the children from the NICU, 82% had bilateral ANAD and 18% were identified with unilateral ANAD. Of the children from the well-baby nursery, 43% were identified with a unilateral ANAD and 57% were identified with bilateral ANAD. Because about one child in almost 70 000 births (the annual birth rate in the State of Colorado) was identified with ANAD from the well-baby nursery, the statistics for unilateral versus bilateral ANAD change slightly with each identified child.

The discussion about developmental outcomes of children with ANAD includes only children with bilateral ANAD. Almost one in every three (32%) children identified with bilateral ANAD had additional cognitive disability. Two-thirds of children with cognitive delays had very significant and often multiple cognitive, neurological, and health issues. Twenty-four percent of children with auditory neuropathy can have normal cognition but other disabilities. Approximately 57% of the Colorado children with ANAD had other disabilities, with over half of them having significant cognitive disorders. About 68% of the children with ANAD had normal cognitive ability, but 36% of these children with normal cognition had hearing loss with additional disabilities.

Thus, children with bilateral ANAD are a complex group of children who frequently have additional developmental disabilities that can include cognitive, motor, vision, and perceptual disorders. They can also have a complex diversity of medical issues. As a result, many of these families receive services from a variety of early intervention providers in addition to receiving services for issues related to hearing.

Thirty-five percent of the Colorado children identified with ANAD were female and 65% were male. In the Colorado data, approximately one of every three children identified with ANAD was Hispanic/Latino, and of them 83% spoke Spanish at home. It was not possible to determine whether environmental factors such as lack of prenatal care or poorer nutrition during pregnancy, socioeconomic factors, or genetic factors were related to this high proportion of Hispanic/Latino children. However, only about one-third of the families identified as Hispanic/Latino in our current population reported that they speak Spanish at home. The 83% of Hispanic/Latino children with ANAD is significantly high in relation to the total population served, leading to the hypothesis that, in this case, prenatal and birth medical issues, such as nutrition, prematurity, birth weight, and hyperbilirubinemia, may be the most significantly related causes for the diagnosis of ANAD.

Eighty-four percent of the families of children with ANAD chose to learn sign language in addition to focusing on spoken language, and one (3%) family chose to communicate with their child through cued speech.

By 3 years of age, 55% of the children with ANAD had language developmental quotients within the average range for children with normal hearing, although many had low average and borderline quotients. Of the children with normal cognition, only 8% were unable to attain and maintain language developmental quotients in the normal range.

Amplification considerations

In the Colorado population that we studied, 76% used hearing aids, 14% did not use any amplification aids, and about 11% had CIs. This low proportion of children with CIs was because this study included children from 2002 to 2009, when CI for children with ANAD had different candidacy criteria than today. Initially, children with ANAD had to present with a profound hearing loss in order to be considered for implantation, whereas now the criteria have broadened to include all levels of hearing loss.

Parents/families and audiologists must consider whether amplification aids should be used. Some children with ANAD have normal auditory thresholds. They may be able to develop age appropriate language and communication skills without the use of amplification aids. However, many children with ANAD face significant difficulty functioning in noisy environments. Children who have not used personal amplification aids may choose to use Frequency Modulation assistive listening (FM) technology to assist in receiving information in noisy environments. Parents/families typically have a hearing aid trial and clinicians and families try to determine whether the children are candidates for CI. An assessment tool, the Infant Monitor of Vocal Production (IMP), developed by Professor Robin Cantle Moore involves an interview that is conducted three times within the first year of a child's life. The first assessment is typically done at about 4-5 months of age before the normally hearing child starts using auditory feedback to monitor vocal production, then sometime around 7-8 months of age when the child starts using auditory feedback to monitor vocal production, and again at 10-11 months of age when the child begins to use what she or he hears to produce meaningful language, the emergence of real words.

The IMP is quite useful in children with ANAD to determine whether the child is making appropriate transitions and integrating auditory perception with vocal production to produce meaningful language. IMP is helpful in determining whether the auditory abilities of the child are moving toward the production of meaningful language. When the child is not using audition for either vocal production or for the production of real words, she or he is likely a candidate for a CI.

Communication opportunity

Families/parents also begin to consider the communication approaches or opportunities before them. Most families have a goal for their children to communicate through spoken language. However, the route to spoken language may include learning visual communication such as cued speech or sign language. Although the child may have excellent auditory skills under quiet conditions, noisy situations may cause a complete inability to access information auditorially. Children with ANAD frequently express that they face significant challenges in noisy situations. The use of FM technology, visual communication such as sign language or cued speech, or speech reading will help assure that the child has optimal access to knowledge and information.

The use of sign language or cued speech may be compromised by other conditions such as cortical blindness or sensory visual impairment and blindness. Visual communication systems require visual perception, visual discrimination, and for communication require motor ability. Children who are deaf or hard of hearing with cerebral palsy may be unable to communicate through sign language or cued speech and may require communication boards or other technology. Children who have difficulty imitating gestures may also have difficulty with sign language use. Children who are deaf or hard of hearing and also autistic may not look at the other communicator. Facial expression and body language are very important in the use of sign language. Cued speech additionally requires that the individual integrate information from speech reading cues with hand cues to identify the phonemes/words produced.

Intervention considerations for auditory spoken language

The development of auditory spoken language requires that the child have access to the sounds of their native language. Some children with ANAD reveal variations in their ability to hear and process sound. Clinicians often refer to their behavior as having 'good hearing days' and 'bad hearing days' or 'good hearing times' and 'bad hearing times'. When this situation occurs, children may sometimes be able to access and process spoken language and at other times may seem unable to hear or understand. In those situations, the use or combination of spoken language with visual communication may help the child continue to access spoken language.

Some children with ANAD have difficulty attending to auditory spoken language. The addition of visual communication may assist the child in maintaining attention. The child with ANAD must also integrate the auditory information for the production of spoken language. These features may be seen in children who do not wear amplification aids, in those with hearing aids, and in those with CIs.

Case A illustrates a child with auditory neuropathy or auditory dyssynchrony, with successful outcomes in spoken language

Case study A

Case A is a child who was diagnosed with bilateral ANAD at 18 months of age. He was not born and screened in the state of Colorado. He had profound bilateral ANAD and showed no response on the Auditory Brain Stem Response test with a robust cochlear microphonic. He was deemed to be a candidate for CI and was implanted unilaterally when he was 20 months of age. He received a second CI at 23 months of age.

Vocabulary

At 6 months after implant activation, he produced 154 vocabulary words of which 83 (54%) were signed and 67 (44%) were spoken. At 12 months after activation, he produced 297 words of which 32 (11%) were signed and 82 (27%) were spoken only and 185 words (62%) were both spoken and signed.

Productive syntax

At 6 months after activation, case A produced 115 utterances of which 53% were with sign language and 70% were with spoken language, sometimes accompanying his sign language. His mean length of utterance in words was 1.08. He used 81 spoken words and 63 signed words. Of the 81 spoken words used, 37 were different, and of the 63 signed words 29 were different. At 12 months after activation, case A produced 248 utterances of which 66 (27%) were signed and 238 (98%) were spoken. He had an mean length of utterance (MLU) of 2.22. He used 289 words of which 89 were different words; 69 of these 289 words were in sign language and 40 of the 69 signs were different signs. Fifty-five of the 69 signed words were also accompanied by intelligible oral speech.

Intelligibility of speech production

At 6 months after activation, case A was unintelligible. He produced 14 vowels that were 51% correct and nine consonants that were 35% correct. By 12 months after activation, his speech was still judged unintelligible. He produced 12 vowels that were 16% correct and 13 consonants that were 32% correct.

Language tests at 6 years

At 6 years of age - 4 years and 4 months after implantation - the Clinical Evaluation of Language Functioning was administered. His scores for Sentence Structure, Word Structure and Expressive Language were all at age level and his Standard Score for Core Language was 98 at the 45th percentile. He was judged to be a fully intelligible speaker by parents, teachers, and coders. He has fully integrated into the typical classroom and is currently not receiving additional services.

Case B was born in the well-baby nursery. His parents spoke a language other than English at home and the mother had a graduate degree and the father a college degree. He was diagnosed with ANAD.

At 20 months, Case B seemed like an optimal ANAD candidate for CI. However, thresholds via evoked compound action potentials through neural response telemetry were not obtained, making mapping of the CI very challenging. After implantation, case B made minimal progress in auditory skills and spoken language and in visual skills and sign language. However, his progress with sign language was stronger than that with spoken language.

Cortical evoked auditory potential P1s were obtained before CI. However, a year after implantation, P1s were found to be absent. Case B received a second implant at 47 months. At activation of the second implant, thresholds could be obtained through neural response telemetry. He demonstrated auditory access to high-frequency sounds. Case B and case A received consistent auditory intervention weekly from a highly skilled therapist. At school, case B made progress in visual communication, but minimal skills were demonstrated in auditory skills and spoken language. Case B responded to the Ling 6 sounds.

Language environment analysis (LENA) technology was used to measure the child's daily auditory diet by recording the amount of adult words the child was exposed to in an average day. He was exposed to 23 990 words, which represents an Adult Word Count at the 95th percentile. He responded to these adult words with 674 conversational turns at the 72nd percentile and with 2312 child vocalizations at the 57th percentile. LENA demonstrated that he was being exposed to a rich spoken language environment and that he responded appropriately with a high number of vocal conversational turns and child vocalizations. However, the Automatic Vocalization Analysis of his vocal production indicated that he did not demonstrate the variability or accuracy expected of a child his age. He received a standard score of 73.9, which indicated that he was at the 4th percentile, more than 2 SDs below the mean of children with normal hearing and typical vocal development.

Case B was assessed again with CAEP, and during the session P1s were present, then absent, and then present again, indicating a fluctuation in neural synchrony, quite similar to his auditory behavior.

Though he appeared initially to be an outstanding candidate for CI, the evaluations indicated that even after CI he was experiencing difficulty at the cortical level. Although he had access to sound through the CIs, he was unable to use what he heard to acquire spoken language.

Case B is an example of a child who appears to have a central auditory processing problem that is so profound that he does not indicate any progress toward the development of listening and spoken language. Fortunately, his family also exposed him to visual communication, and, although he is experiencing some perceptual difficulties with visual communication, it is still stronger than his auditory perceptual skills and he has developed a communication system. Most of his utterances are single words.

Case B continues to face challenges in language development and communication and is predominantly a visual communicator. However, he has developed signed vocabulary, although he experiences significant challenges in the development of sentence structure. He is an example of a child who would have no communication skills if his sole avenue of communication had been listening and spoken language.

Case C represents a child with significant comorbidities

Case C was identified at 10 months and began receiving early intervention services at 11 months of age. He is not using amplification aids and he has been identified as a child with severe to profound hearing loss bilaterally. He was premature at birth and sustained brain damage resulting in cerebral palsy, severe developmental and cognitive delay, and sensorimotor integration problems. In addition to CHIP early intervention services, he receives intervention from physical and occupational therapists and his family receives services from a sign language instructor. He also has chronic lung issues. His comprehension and expression of language is at a language quotient of about 67. Because his motor delays compromise the ability to assess his true cognitive abilities, language communication abilities are his highest measured developmental score.

Using the Functional Auditory Profile Indicators, his auditory skills were followed longitudinally. By 33 months, he showed consistent responses to the detection, meaning, and auditory feedback subscales with 100% mastery of the first two subscales. By 33 months of age, he had made excellent progress in auditory discrimination with an almost 80% mastery of the items in this subscale. His vocal production of vowels and consonants was inconsistent and ranged from 8 to 11 different vowels and 6-8 consonants. Motor speech difficulties interfered with his ability to produce phonemes, although his auditory discrimination skills indicated that he could discriminate the phonemes.

Case C communicates through vocal production and sign language. He has also used a variety of communication devices for children with cerebral palsy. Despite his multiple comorbidities, he is making excellent progress in his auditory skill development. Spoken language development is significantly impacted by his other involvements.

Conclusion

These three cases demonstrate the complexity and diversity of children with ANAD. However, children can experience success in communication development with the use of CIs, hearing aids, and other communication devices, as well as without hearing aids. They can also demonstrate success using visual communication such as sign language or cued speech.